A lens is cut into two equal halves: Along the principal axis.
What will be the focallength of each half?

Write the formula for a lens connecting image distance (υ), object distance (u) and the focal length (f). How does the lens formula differ from the mirror formula?

List four specific characteristics of the images of the objects formed by convex mirrors.

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?

A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

An object of height 2.5cm is placed at a distance of 15cm from the optical centre ‘O' of a convex lens of focal length 10cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘O', principal focus F and height of the image on the diagram.

List four precautions which a student should observe while determining the focal length of a given convex lens by obtaining image of a distant object on a screen.

Name the lens which always forms a virtual image of an object.

Explain why, a real image can be projected on a screen but a virtual image cannot.

Draw diagram to represent the action of a concave mirror on a beam of parallel light rays. Mark on this diagram principal axis, focus F, centre of curvature C, pole P and focal length ƒ, of the concave mirror.